Marine scientists from California are venturing this week to the middle of the North Pacific for a study of plastic debris accumulating across hundreds of miles (km) of open sea dubbed the “Great Pacific Garbage Patch.”

A research vessel carrying a team of about 30 researchers, technicians and crew members embarked on Sunday on a three-week voyage from the Scripps Institution of Oceanography, based at the University of California at San Diego.

The expedition will study how much debris — mostly tiny plastic fragments — is collecting in an expanse of sea known as the North Pacific Ocean Gyre, how that material is distributed and how it affects marine life.

The debris ends up concentrated by circular, clockwise ocean currents within an oblong-shaped “convergence zone” hundreds of miles (km) across from end to end near the Hawaiian Islands, about midway between Japan and the West Coast of the United States.